Methods for production of double-walled carbon nanotubes

Abstract

The present invention relates to fullerene carbon nanotubes having a cylindrical wall comprising a double layer of carbon atoms and methods for the production and application of these double-wall carbon nanotubes; and, more particularly, to nanotubes with controlled number of carbon layers and methods for the production of macroscopic amounts of these nanotubes and there application as cathode materials in the cold field electron emission devices, notable such devices comprising light emitting CRT's.

1. A method of producing fullerenes comprising double walled nanotubes (DWNTs) via catalytic chemical vapor deposition which comprises
 (a) providing a source of carbon and a catalyst comprised of transition metal of the iron group of the periodic table of the elements and sulfur in the presence of a hydrogen containing gas and an inert gas in a reaction zone having a DWNT forming atmosphere; (b) heating said source of carbon and catalyst in the presence of said hydrogen containing gas and inert gas in the DWNT forming atmosphere in the reaction zone under conditions effective to produce hot carbon counting vapor and to obtain DWNTs, when said vapor is quenched; (c) quenching the hot vapor in said DWNT forming atmosphere, thus condensing the hot vapor to form a product comprised of DWNTs; and (d) collecting the resulting product and recovering said DWNTs from the resulting product outside the heated region of the reaction zone, wherein the catalyst mixture is comprised of 27% iron, 14% cobalt, 51% nickel and 8% sulfur, by weight. 
 
     
     
       2. A method of producing fullerenes comprising double walled nanotubes (DWNTs) via catalytic chemical vapor deposition which comprises:
 (a) providing a source of carbon and a catalyst comprised of transition metal of the iron group of the periodic table of the elements and sulfur in the presence of a hydrogen containing gas and an inert gas in a reaction zone having a DWNT forming atmosphere; (b) heating said source of carbon and catalyst in the presence of said hydrogen containing gas and inert gas in the DWNT forming atmosphere in the reaction zone under conditions effective to produce hot carbon counting vapor and to obtain DWNTs, when said vapor is quenched; (c) quenching the hot vapor in said DWNT forming atmosphere, thus condensing the hot vapor to form a product comprised of DWNTs; and (d) collecting the resulting product and recovering said DWNTs from the resulting product outside the heated region of the reaction zone, wherein the DWNT forming atmosphere contains a mixture of elemental hydrogen and argon gases, and at least one of the gases selected from the thiophene vapor, hydrogen sulfide, carbon disulfide and methane is added thereto, and wherein the gas mixture is pyrolyzed over a supported or floating metal catalyst and wherein catalytic pyrolysis is accomplished by utilizing inductively coupled high frequency plasma in a flow-through tubular reactor at reduced pressure, instead of thermal heating of gas flow. 
 
     
     
       3. The method of  claim 2 , wherein the catalyst is comprised of a mixture of particles of iron, cobalt, nickel and sulfur that is subjected to the preliminary step of heating under temperature and condition suitable to cause a reaction between the sulfur and the other metals of the mixture, thereby producing sulfides of said metals and wherein the powder comprising said catalyst is dispersed in the influent gas and thus delivered as a floating catalyst into a plasma region of vertically installed tubular reactor.